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The newest geological history of Armenia
On the basis of generalization of materials of complex researches in the monograph are grounded the following main scientific regulations that are first elaborated.
Main regularities of the nawest geological history are established, a new regional stratigraphic scheme is presented and palaeogeographic events of the upper part of Cainozoic Armenia are reconstructed (table 7, 8).
In Late Miocene, Pliocene and Pleistocene of Armenia are established and traced 29 huge subdivisions, and in Holocene – 12 fractional ones that are corresponded to bio-, climato- and lithostratigraphical units or their parts in accordance with their volume and some of them are marked out in volume of suites, subsuites and beds. The stratigraphic units are marked out on the basis of sedimentary rocks, signs of which are conditioned by rhythmic changes of climate fixed in peculiarities of material composition of rocks and associations of remains of fauna, mainly of plants, with regard for duration of forming stratigraphic unit of corresponding rank.
The borders of stratigraphic units are palaeoclimatic boundaries expressed in the change of lithological composition of deposits, in the replacement of associations of climatic and ecological indicators – fauna, flora, Diatoms, geochemical environment and others. The stratigraphic units of the territory of Armenia are correlated and projected for the general scale.
Since the epoch of drawing of the territory of Armenia in a continental stage of development (the end of Sarmatian – the beginning of Meotian) have been marked out 10 big erosion-sedimentary cycles: at the end of Sarmatian – Meotian, Pontian, Cimmerian, Akchaghylian, Eopleistocene (2), Neopleistocene (3) and Holocene. These cycles occurred in an obvious dependence on tectonic elevations and their relative stabilization as well as climatic changes. Each of these cycles began with a big phase of tectonic rising of the region, down-cutting, alluvial sedimentation, cold then a new phase of elevation of the region and erosion followed. The clear regularity has been established: lacustrine deposits were formed during the epochs of relative tectonic stabilization, cold snap, humidification and afforestation of the region, and alluvial ones – in the epochs of stirring up tectonic movements (elevations), down-cutting, growing warmer (aridity), xerophytic steppification. There was a direct dependence of erosion – sedimentary cycles of the Quarternary period on changes of the main basis of erosion – level of the Caspian Sea: the epochs of cold snap and humidification corresponded to transgressions of the sea in Armenia, and epochs of growing warmer and aridity – to regressions.
Since Late Sarmatian the natural process has been proceeded within the limits of direct general climatic cold snap that was growing in the Quarternary period on the territory of Armenia. A cold snap was progressing from Pleistocene to Eopleistocene and Neopleistocene in the second half of Cimmerian, in the last periods of Akchaghylian, Apsheronian, Early, Middle and Late Neopleistocene. Eopleistocene cold snap was connected with the epoch of cold snap of the Russian plain. For Middle and Late Neopleistocene of Armenia are established two stages of cold snap and humidification divided by growing warmer as well as two stages of development of mountainous glaciers divided by interstadials. The phases of stirring up river outflow and forming of coarse-grained alluvium were submitted to dynamics of a snow line in the periods of development of two stages of glaciation. These stages could be connected with two stages of cover glaciations of the Russian plain – Dnieper and Valdai.
Thus, the main point of the natural process on the territory of Armenia for the last 11million years is that on the background of long one-directed development, which comes to gradual cold snap, rhythmical changes of natural environment on the whole and all its separate components took place. The natural process on the whole territory reflected synchronically in regional and interregional scales and at the same time was submitted to the laws of ubiquity, direction, rhythm, local (regional) individuality.The elaborated scientific propositions and a new scheme of stratigraphy and palaeogeography of Late Miocene, Pliocene and the Quarternary period of the territory of Armenia can be used for qualitative conducting of geological mapping of different scales for ground, estimation and search of some useful minerals (building materials, fresh waters, placers and others), for neotectonic, geodynamic and microseismic zoning, for engineering-geological ground of building objects and can promote the decision of some ecological aspects of landscape-climatic prognosis of the future as well.
Academy National of Sciences of Armenia Pub. “Gitutyun” Yerevan 2009